This document outlines rules for designing starships for
a science fiction role-playing game. It is heavily influenced by the Traveller
High Guard ship design system, and features a roughly similar level
of detail. It tends to be slightly more math-intensive, but with an appropriate
spreadsheet, a ship can be designed, tweaked, and finalized within only
a few minutes.

The starship operations and combat rules for the system
have not yet been developed, though certain features of the design system
imply details of the combat system.

Many of the traditional types of Traveller ships (Scout/Couriers,
Free Traders, Close Escorts) can be closely approximated in this system,
though some important details will differ. A good way to start using the
Sohl Cluster design system is to convert an existing High Guard
design.

Metrics

Five primary metrics are tracked in the design system:
tonnage (mass), cost, power, computing, and crew.

Tonnage, unlike in High Guard, refers only to mass,
not volume; translating tons to deck plan squares is thus less straightforward.
The overall tonnage of the ship is selected, and each component (including
the hull framework) contributes toward that tonnage. Modular designs, dismountable
fuel tanks, and external cargo should be handled by constructing the ship
in its most massive possible configuration; only maneuver drive performance
will change in other configurations, and is easily recalculated. Tonnage
is measured in metric tons (or tonnes, if thatís your preference).

Cost for all components is specified per ton of component.
Costs as given in the tables are on roughly the same order of magnitude
as those in High Guard. Obviously the cost values can be easily
altered to suit the campaign. Cost is measured in megacredits (MCr).

Power is the equivalent of High Guard energy points;
itís what is produced by the power plant and consumed by other components.
By convention, the power requirements of all of a shipís systems are totaled,
then rounded up to the next whole number to determine the expected capacity
of the shipís power plant. It is naturally legal to build a power plant
which delivers a non-integral number of power points, or a power plant
which does not provide full power to all systems simultaneously, but it
is required that such deviations are well-documented. Power is measured
in abstract power points. An assumption that a power point is equivalent
to a High Guard energy point and thus equal to about 250 megawatts
is not unreasonable.

Computing is a resource consumed by most ship systems
(rather than only a few, as in High Guard) and provided by shipsí
computers. As with power points, it is conventional to total the computing
requirements of all of a shipís systems, then round up to the next whole
number to determine the expected capacity of the shipís computer. Computing
is measured in abstract computing points which imply a mixture of processing,
storage, networking, and I/O capability; a single computing point is far
more power than a typical home computer.

Crew is similarly a resource demanded by most ship systems;
the small fractions of a crew member are added up and (naturally) rounded
up to a whole number of people. Actual assignments of individual crew to
required roles are left up to refereeís discretion; in practice, despite
what the spreadsheet may imply, a single crew member generally doesnít
spend his time on several different jobs. As an example, the standard scout
ship crew requirements include 1.24 crew for the warp drive, 1.0 crew for
the power plant, and 0.84 crew for the maneuver drive; the likelihood is
that each station gets exactly one crew member. Additionally, crew positions
can be automated, which requires a great deal of computing power, but reduces
life support needs. Ordinarily, no more than half the crew may be eliminated
by automation, rounding down, but for things like unmanned probes with
very limited decision-making capability, or remote-controlled vessels,
the entire crew complement may be eliminated.

Hull

The hull frame component masses a flat percentage of the
final ship tonnage; this includes a pressurized interior, at least one
airlock per 100 tons or fraction of hull, and the framework to attach all
other components to, and attitude controls via gyroscope and/or reaction
jet. Typically, almost all components are in the pressurized section of
the ship, though this is not required. Incidentally, in these rules, unlike
Traveller, there are no rules changes at the 100-ton mark, yet High
Guard ships and small craft tend to convert fairly straightforwardly
at their former tonnage, mainly by the method of reducing small craftís
endurance. Hulls do not require power or crew, though stealthy and deceptive
hulls require computing.

By default, the hull is unstreamlined; it cannot enter
an atmosphere or skim gas giants for fuel. Partial, full, or airframe streamlining
may be purchased at additional cost and tonnage. Partial streamlining allows
gas giant skimming and entry into a very thin atmosphere. Full streamlining
allows gas giant skimming and entry into any atmosphere. Airframe streamlining
not only allows safe entry into any atmosphere, but provides airfoil and
control surfaces which effectively double the power of the maneuver drive
in dense or standard atmosphere. In other words, a fully streamlined ship
with a 1-g motor cannot land safely on a 1.8-g world with a standard atmosphere,
but an airframe ship can.

A stealthy hull configuration uses special materials and
hull shapes to make a ship harder to detect. In addition, the shipís computer
and passive sensors conspire to keep the ship oriented in such a way as
to minimize its visibility to active sensors (i.e. turning the minimal
cross section towards the emitter).

A deceptive hull configuration makes the ship appear to
be something it is not. It can make a warship look like a liner or vice
versa, look like higher or lower technology than it actually is, or make
a ship look like a planetoid. It can even make a ship built by one company,
culture, or species look like it came from another. Deceptive configuration
can be bought multiple times Ė a high-tech alien warship can look like
a low-tech terran liner for the cost of 3 deceptive configurations. Apparent
tonnage canít be altered more than about 15%, and actual performance isnít
altered. This deception is fixed at design time, but for one extra "level
of deception", the ship can morph between two configurations.

Armored hulls include both internal and external structural
improvements. The cost is per "armor pip", and the as yet undeveloped
combat system will specify how armored hulls affect battle; the effect
will probably be comparable to High Guard armor.

Maneuver Drives

Sohl Cluster offers three fundamentally different types
of maneuver drive: reaction, gravitic, and reactionless. Combinations of
the three may be purchased and can operate together, adding their effects.
All three of them have a base cost plus a per-gee, per-ton cost. Maneuver
drives are usually bought in whole gee numbers, but may be bought in tenths
of gees. All three require power, computing, and crew. Only reaction motors
consume fuel directly.

Reaction motors are cheap and consume large amounts of
fuel. They also create a large, easily detected trail in space. They are
hazardous; many worlds may have restrictions on in-atmosphere use of reaction
drives. It is not uncommon for a large ship with a weak gravitic or reactionless
drive to have a small "booster" reaction motor with a small fuel
supply to assist in takeoffs and landings from high-gravity worlds; a half-day
fuel tank is usually sufficient for one takeoff and one landing.

Gravitic drives are fairly efficient, but their gee potential
is multiplied by the gee distortion of local space. Thus, a 1-G gravitic
drive canít take off straight up without a streamlined hull, but can easily
enter and leave orbit from space, and far away from any planets, will have
almost no maneuvering ability. Piloting a gravitic ship is harder than
using a reaction or reactionless drive; it is akin to sailing a wind-powered
vessel as opposed to a motorboat. They do not emit any detectable exhaust.
A "2-G" (or any other value) gravitic drive is a slight misnomer;
itís a "times 2" drive, which provides 2G only when located in
a 1G gravitational potential region.

Reactionless drives are expensive and complex, but they
donít require a fuel supply, they arenít dependent on the local gravity
well, and they donít emit harmful or detectable exhaust.

"Compact" reactionless and gravitic drives,
but not reaction drives, can be purchased. These have 1/10 the usual base
tonnage, but the usual per-gee/per-ton costs. They cannot be repaired except
at a well-equipped base, or aboard a ship with a maintenance hangar equal
to 100 times the tonnage of the compact drive to be repaired. These are
intended primarily for very small vehicles.

Power Plants

Sohl Cluster provides two types of power plants, which
require fuel to generate power, and batteries. Fusion and antimatter reactors
have a base cost, per-power-point cost, and fuel tankage cost. Batteries
only have a per-point-per-day cost. A ship with both reactors and batteries
can divert small amounts of power to recharging its batteries; a ship with
batteries only must be recharged by a starport or another ship.

Fusion reactors are fairly cheap and consume moderate
amounts of fuel. In operation, they produce a very small amount of emissions
which are detectable by nearby ships.

Antimatter reactors are expensive and bulky, but are far
more fuel-efficient. They emit more detectable radiation than fusion reactors.

Batteries are more efficient than reactors for short durations,
and so are frequently found in small craft. They emit no detectable radiation,
and as such, they are well-suited for installing in stealthy ships.

Fuel is bought per point per day. It is therefore very
straightforward to trade off tonnage for endurance when tuning a design.
The Traveller convention is to allocate fuel for 30 days of power.

If antimatter power plants are abhorrent to the nature
of the campaign, they can be called "highly advanced fusion plants".

Faster than Light Drives

Sohl Cluster assumes a "warp drive" style FTL
drive rather than Travellerís jump drive; this can be altered according
to the requirements of the campaign. The assumption is that "warp
class one" can travel about one parsec every 20 days (~60 c), and
higher warp classes show a linear progression in speed. Warp drives may
be installed in ships under 100 tons; useful probes and courier ships can
be built in the 30-50 ton range, or even smaller with advanced technology.
Warp drives do not require fuel other than that required for the power
plant, but they do require power, computing, and crew.

A ship in warp drive cannot be interacted with, but it
emits a distinctive spectrum of electromagnetic radiation which can be
easily detected. Of course, the ship is moving at least 60 times faster
than that emission! A ship can start or stop warp drive on about 15 minutesí
notice at any time, and thus can drop into real space at the edge of a
system, use its sensors, then proceed deeper into the system on warp drive.

A warp drive requires at least 30 minutes of "preheating"
before use, which requires its full energy point budget. This should discourage
building ships without enough power capacity to simultaneously use warp
and maneuver drives; such ships are unable to dodge enemy fire while preparing
to enter hyperspace.

All crewed ships, including small craft, require a bridge.
A bridge has a base and a per-ton-of-ship cost. Unmanned vessels with completely
automatic programs (probes, etc.) can omit the bridge. Any bridge can function
as a flag bridge (i.e. allow the ship to operate as a combat group leader),
but the number of other ships in the group cannot exceed twice the base-10
exponent of the shipís tonnage (i.e. a 100- to 900-ton ship can lead up
to 4 other ships; a 10000-ton ship can lead up to 8 other ships). Larger
group control can be achieved by buying the bridge multiple times; each
additional bridge adds the base group size again; a 10000-ton ship with
a triple-size bridge can lead 24 other ships. The additional space largely
consists of tactical displays showing the situation with respect to other
ships in the group, and communication stations to better coordinate with
the captains of the other ships. Multiple purchases of bridge must be designated
as "flag bridge" which adds to the leader capability, or as "emergency
bridge" to back up the main bridge. Emergency bridge may also include
flag capability. In other words, if you buy 5 times the basic bridge requirement,
you must specify if itís 5 separate standard bridges, a single bridge with
5x lead capability, or a 3x bridge with a 2x emergency bridge.

Vehicles with no advanced navigational requirements can
opt for purchasing Basic Controls instead of the bridge base cost. Basic
controls cost 1/10th of the base tonnage of a starship bridge,
but have the same per-ton-of-ship cost. Vehicles with basic controls cannot
use sensors for anything except basic detection of other objects; they
cannot have any fire control stations or weaponry installed; they have
no group leadership ability. Thus, basic controls are only suitable for
atmospheric vehicles such as aircars or Gcarriers, or possibly spacegoing
lifeboats.

Every weapon battery requires a fire control station,
with a flat per-station cost. Weapon batteries must consist of a whole
number of identical weapons. Weapon batteries are defined at ship construction
time.

Active and passive sensors have per-class costs. Higher
sensor classes are more sensitive and more likely to detect objects in
space. The exact effect of sensors on combat must await the development
of combat rules.

Active sensors work by emitting electromagnetic radiation
and detecting the reflected radiation. Any ship using active sensors can
be detected by any ship with passive sensors within a very long range.
A typical warship will have a class 5 or better active sensors; civilian
and auxiliary ships will usually have class 4 and under. Active sensors
greatly improve target tracking in combat, but expose a shipís position
when in use.

Passive sensors detect radiation emitted and reflected
from other sources. A typical warship will have a class 5 or better passive
sensors; civilian and auxiliary ships will usually have class 4 and under.
Stealthy ships, and ships designed to hunt them, tend to have very good
passive sensors. Passive sensors can be used for target tracking, but are
less accurate than active sensors.

Computers and Automation

Many components require computing power, which is provided
by installation of a computer. Note that computers require power and crew
in turn. Itís worth noting that power plants have no per-point computing
requirement, in order to avoid a feedback loop between computer and power
plant allocation which makes Excel complain.

Crew may be replaced with automation. The cost is per
replaced crew member. For full function of a ship, no more than half the
crew, rounded down, may be replaced. This doesnít become tonnage-efficient
until very long missions are involved. If human judgement isnít required
for a mission (i.e. if a single written page suffices to describe its behavior),
the entire crew can be replaced; this provides for unmanned courier drones
and the like. Adding automation increases computing requirements, which
can increase crew size, which can allow more crew positions to be automated,
so a couple of iterations through the spreadsheet may be necessary to optimally
automate a crew.

Optionally, if Travellerís "Solo Scout" concept
is important to the campaign, automation between 50% and 100% of the crew
can be allowed, but there will be indirect effects on the efficient running
of the ship. It may take longer to perform certain tasks; first-class passengers
wonít be impressed with the cabin service; the need to dodge enemy fire
might make it impossible to concentrate on plotting a safe hyperspacial
trajectory, etc.

Cargo and Vehicles

Cargo space is designated for free; vehicle facilities
are designated at 1.1 tons per ton of vehicle regardless of whether the
vehicle is carried internally or externally. Vehicle crews should normally
be designated as extra crew in the carrying shipís complement.

Crew and Passenger Accommodation

Crew and passenger accommodation has a base cost per person
and a cost per person per "comfortable day". Time spent aboard
ship beyond the comfort period requires a morale check every time half
the original comfort period elapses. For example, a ship with 30-day accommodations
will require morale checks at 45 and 60 days. Morale failures may result
in penalties to job performance or interpersonal confrontations. Repeated
morale failures can result in psychotic episodes ("space rage"
or "cabin fever"). After twice the original comfort period, the
ship will be on short rations. After three times the original comfort period,
all food will be gone (exception: ships with 120 day or more comfort periods
are assumed to have recycling systems; no one will starve, but the food
will be unappealing).

Different classes of passenger and crew have different
accommodation needs. "High Passage" or First Class passengers
require 1.5 comfortable days allocated for each day spent aboard ship;
if necessary, they will "rough it" at 1 day allocated per day
spent, but will demand a 50% discount. "Middle Passage" or Second
Class passengers require 1 comfortable day allocated for each day spent
aboard ship; they will "rough it" to 0.75 days allocated at a
50% discount. Starship crew officers require 1 comfortable day allocated;
they will rough it to 0.5 days allocated for an additional 15% pay. Non-commissioned
starship crew require 0.75 comfortable day allocated per day, and will
also go to 0.5 days for 15% extra pay. Beyond those time periods, passengers
will not pay at all, and crew will negotiate for as much extra pay as they
can get (if they donít fail morale checks) or refuse to work (if they do
fail).

A 5-day crew accommodation may be designated as
a "Low Berth" or suspended animation chamber; this will keep
one human alive, well, and unconscious for any length of time. This is
a very cheap but unpleasant and sometimes risky way to travel.

Weapons

Weapon specification is pretty abstract, and can be tuned
to the needs of the campaign. Since the combat rules are undeveloped, the
following items outline the basic facts:

The basic weapon flavors are "beam" and "missile".
Missiles require ammunition and are more accurate at medium to long range;
beams require power points and cannot hit at medium to long range. Lasers,
particle accelerators, plasma guns, fusion guns, and meson guns are all
simply "beam" weapons. If more weapon types are desired a la
High Guard, then particle beam guns can be designated at double
cost, and meson guns at triple cost, with certain damage effects in combat;
nuclear missiles and sandcasters are simply different ammunition types
for missile launchers.

Either beams or missiles may be mounted in turrets or
in fixed mounts. Fixed mounts fire forward only, the pilot is the gunner,
and there is a substantial penalty to hit for fixed beams. Turret mounts
can fire in a nearly-hemispherical arc, and are manned by gunners (usually
remotely).

Weapon class is a exponential scaling-up of the weapon
that affects all costs of the weapon equally, each class being double the
size of the next lower class: a class 2 beam masses and costs twice as
much and requires twice as much power and computing, etc., as a class 1;
a class 3 is 4 times the cost of a class 1, etc. The maximum class of a
weapon is 10.

Unlike Traveller, there are no hard limits to the total
number of weapons that can be mounted on a ship of a given size. Power
plant, ammunition, crew, and fire control requirements do provide implicit
limits.

Up to ten identical weapons can be grouped into a weapon
battery; a single fire control station controls a single battery. A fire
control station is required even for fixed mount batteries. Only one fixed-mount
battery on a ship can be fired in a combat turn. Fire control stations
may be associated with different batteries at different times, but batteries
themselves must be designated at ship design time.

Any turreted beams or missiles can be used in the anti-missile
role.

Multiple classes of the same flavor of weapon may be
installed (e.g. class 4 beams for offense and class 1 beams for anti-missile
use).

No missiles are held in the launcher itself. Missiles
each mass 1/10 the mass of the launcher, and as such, add up pretty fast.
All missiles of a given class aboard ship are assumed to be in a common
magazine, and can be fired from any battery. The magazine cost provides
storage and automatic loaders. The missiles themselves cost Cr50000 (MCr
0.05) per class, each, for standard missiles. Sandcaster missiles cost
50% of that (Cr25000 per class). Nuclear warhead missiles cost at least
4 times standard (Cr200000 per class).

Class-1 and -2 beams and missiles are roughly equal in
power to Travellerís turret and barbette weapons. A single class-4 weapon
is roughly equal to a High Guard (1st edition) 10-ton
bay. A battery of 3 class-5 weapons is roughly equal to a High Guard
50-ton bay weapon. A battery of 3 class-6 weapons is roughly equal to a
High Guard 100-ton bay weapon. A battery of 10 class-10 beams (the
largest battery available in Sohl Cluster) approximates a 5000-ton High
Guard spinal mount (by definition a fixed, not turreted, weapon).

Defenses

Shields may be purchased. The maximum level of shielding
is 20. Shields defend equally against all types of weapons; they are equivalent
to a combination of High Guard nuclear dampers and meson screens
and then some: they protect against lasers and conventional missiles.

Technology Levels (Optional)

Since technology levels tend to be defined very differently
across SFRPG systems, this design system keeps technology levels very simple.
Any component can be built with "primitive", "standard",
or "advanced" technology, except for the following:

fuel

cargo space

vehicle space

crew accommodations

missile ammunition

With "primitive" technology, the tonnage of
the item is multiplied by 1.5 and the cost per ton is multiplied by 0.5
(yielding an overall cost factor of 0.75).

With "standard" technology, the tonnage and
cost of the item is unchanged.

With "advanced" technology, the tonnage is multiplied
by 0.75 and the cost per ton is multiplied by 4.0 (yielding an overall
cost factor of 3.0).

Component technologies may be mixed and matched, even
to the point of putting primitive per-gee-per-ton reaction drives in ships
with advanced reaction drive bases.

Converting Traveller TL to Sohl Cluster component availability
is left as an exercise for the GM.

Deck Plans

The Traveller convention of "two 1.5m deck squares
equals one ton" no longer applies; a ton is mass and not volume in
Sohl Cluster. Machinery is far denser than liquid hydrogen, and so probably
rates one square or less per ton, plus access space. Crew accommodations
probably should still be constructed at two squares per ton. Fudge as required
Ė thatís what you do anyway, right?

Example Ship: The Scout/Courier

As an example, consider the translation of the venerable
"Type S Scout/Courier" from Traveller terms into Sohl Cluster.
Download the spreadsheet to see how I chose
to do it.